1. Field of the Invention
The present invention relates to an improved vacuum cleaning apparatus. The present invention relates to improvements wherein a vacuum cleaning apparatus does not need to be shut off in order to remove the dirt filled container and can in fact continue vacuum suction at an undiminished rate during removal of said container. The present invention further provides a multiplicity of dirt capturing chambers which can be removed sequentially without affecting the vacuuming process, thereby increasing to infinity the cleaning capacity of the vacuum cleaner system. The present invention further relates to a system for prolonging the life of the vacuum cleaner filters by reducing the amount of dirt and debris that can clog the matrix or the pores of the vacuum cleaner filter itself.
2. Description of the Prior Art
Vacuum cleaners are machines designed to suck in dirty air or other fluid containing particles for the purpose of (1) trapping the dirt or particles to be discarded and resulting in clean air or fluid to be recirculated, or (2) increasing the concentration of the particles or contaminants suspended in air or other fluids for further forensic, medical or chemical analysis, or recycle. For these purposes a vacuum cleaner typically consists of (1) an inlet hose where the air or fluid is sucked in, (2) a filter bag or filtration means with effective pore sizes suitable for separation of the particles from the surrounding fluid phase. After separation, the separated particles would be retained within the interior of the filter bag. (3) a motor usually behind the filtration means to draw the dirty air or particle suspension into the inlet hose and through the filtration means, after which the cleaned air or fluid leaves the vacuum cleaner, and (4) a rigid housing for the filtration means and the motor and connection to the inlet hose.
However, conventional vacuum cleaners have several major problems. (1) As soon as the filtration means starts to work, separating the particles from the fluids by means of trapping the particles via the pores of the filter, the number of pores effective for further filtration decreases. This means the efficiency of filtration drastically decreases even though the motor is working at maximum power. (2) As the filter bag or filtration means gets clogged up, it has to be changed, cleaned or discarded. This not only involves the cost of the bag but requires interruption of the vacuuming process. In many situations even temporary termination of the suction process is not desirable. For example, in large built-in vacuum systems such as for use in hospitals or in organic farming (e.g. to remove caterpillars and insects from lettuce) where many workers over a wide area need constant vacuum power at all times, the motor simply cannot be turned off for the purpose of changing filled up filter bags. (3) When the motor needs to be turned off for the purpose of changing filter bags, no matter how temporary, part of the contaminant may become loosened from the filter surface and recirculate back to the open air because there is no pressure at the time to keep the dirt onto the surface of the filter. In the cement or other construction material manufacturing industry where light powder-like material is involved, this means the workers will have to wear masks to prevent breathing in the particles during the changing of filter bags. In hospital settings, where viral particles or other infectious diseases abound, rebreathing of concentrated infectious agents is a distinct occupational and health hazard. Ideally, the filled bags should be changed with the motor still on and filtering can go on without leakage and exposure to the workers involved. (4) The filtrating process of most vacuum cleaners will trap most of the particles within the matrix or pores of the filters. This is not desirable if the purpose of filtration is to recover, not to discard, the particles for further analysis. The reason is because most of the material cannot be recovered from the filter matrix. In addition, for materials that are sensitive to compacting pressure, the positive pressure pressing the particles into the retention surface of the filter may denature them and change their properties. Positive pressure here is defined as a pressure in the direction towards the retention surface of the filter. Positive pressure tends to bring the particles towards the filter and press them against the retention surface of the filter. With this definition, a "vacuum" source (defined as pressure less than atmospheric pressure) drawing dirty air towards the interior surface of a vacuum cleaner filter bag actually exerts a positive pressure on the retention surface of the filter bag. The retention surface of a filter is defined as the surface that faces the material or fluid suspension to be filtered and is the surface facing away from the filtered clean fluid. The interior surface of the vacuum cleaner filter bag for example is the retention surface. For the purpose of simplicity here, we will define as particles any molecules or aggregates whether in dissolved state, solid state or colloidal state, which are dissolved or suspended in a fluid phase, liquid or gaseous, and which can be retained by a filtration means.
Therefore, there exists a need for a vacuuming machine that (1) does not decrease efficiency with use; (2) does not require turning off of the motor for changing filled up bags; (3) prevents recirculation of filtered particles back to the environment; and (4) does not excessively compact or denature the material to be filtered.
Several methods have been attempted, often with unsatisfactory results, to overcome the problems mentioned above.
To overcome the decreased efficiency of one filter bag, several approaches were used:
1. Conventional pre-filters have been used to screen out large particles by virtue of pre-filters with pore sizes much larger than the pore sizes of the filter bag in the vacuum cleaner. The idea is to presieve the material so that only particles of the appropriate size (e.g. dust) for filtration is presented to the filter bag of the vacuum cleaner. Also the load presented for the vacuum cleaner is decreased (e.g. rocks and stones have been removed by the pre-filter). The problems of such an approach are that such pre-filters can clog, and when they clog, even the smaller particles cannot go through to reach the vacuum cleaner. So in reality, such an arrangement is merely utilizing two filters of different sizes in tandem and employing positive pressure (although by a single motor generating a "vacuum source") to filter particles of different sizes.
Even if large particles are pre-filtered out, the small particles can still clog the filter bag of the vacuum cleaner and decrease its efficiency.
2. To promote detachment of clogging materials from the vacuum cleaner filter, some vacuum cleaners are designed with the inlet hose connected near the bottom of the vacuum cleaner unit and the filter fixed at the top so that the movement of dirty air is from bottom to top inside the unit and the clean air then exists near the top of the unit. The idea is to promote detachment of the filtered dirt from the filter means by virtue of gravitational force. It is hoped that when the motor is turned off, the dust particles will fall off the filter means back to the bottom, to be removed at some time later. The filter may or may not need to be removed or changed every time. The disadvantages are: (1) when the motor is turned on, the particles coming from the inlet hose as well as those that have detached and fallen off from previous suction will both clog the filter again; (2) gravitational force will only detach high density particles (e.g. rocks) which normally is not the main obstructive particles of the filter means; (3) removal of filtered material requires turning off the motor and interruption of the vacuuming process; (4) detachment, if any, of the filtered dust from the fixed filter means by gravity promotes dispersion of the dust particles within the storage compartment and therefore when the compartment is opened for removal of dirt, contamination of the environment will result; (5) such prior art uses unopposed positive pressure which tends to compact the particles collected, and is not suitable if the purpose of the filtration is to collect and concentrate particles for further analysis without changing their physical properties.
3. The inventor, Dr. Richard Yen, has filed a copending patent application entitled "Prefilter For Vacuum Cleaners", Ser. No. 07/335,876 filed on Apr. 10, 1989. The inventor's previous patent application of a self-cleaning pre-filter employed a different method which is useful for particles that tend to stick to each other. The principle utilized negative pressures to draw the sticky particles away from the pre-filter surfaces. By using a strong negative pressure, the particles are actually detached or anti-clogged from the pre-filter while they are being concentrated. The concentrating effect promotes aggregation. By allowing a long enough passage in the pre-filter system before the particles reach the main filter bag of the vacuum cleaner, the aggregation of the particles will have resulted in the formation of bigger particles too large to effectively clog the pores of the filter bag of the vacuum cleaner. The idea of such a pre-filter is new in that (1) it does not require the pre-filter to have a particular pore size as compared to the size of the vacuum cleaner filter bag (i.e. does not have to be larger or smaller), (2) the pre-filter is self-cleaned and designed not to trap any particles, (3) the pre-filter utilizes a negative pressure greater than the positive pressure at sites on the pre-filter surfaces where the tendency to clog is greatest, (4) the pre-filter serves to concentrate particles that have a tendency to aggregate into larger particles.
However, for application in situations where the particles do not tend to aggregate, such as (1) dry powder (as opposed to wet powder), or (2) particles with electric charges in the surface that repel each other, or (3) smooth and hard surfaces, or (4) light density and small particles that keep floating and not settling with time; a new design of the vacuum cleaner itself must also be considered. The present application is a novel design of the vacuum cleaner, and can be used in conjunction with, or in the absence of, the inventor's previous invention of a self-cleaning pre-filter or any other pre-filters.